This invention is concerned with a method for preparing cross-linked styrenic polymer articles, for example, trays, containers, flat tableware, egg cartons, etc. and the so-crosslinked polymer articles.
It is well known in the art to produce various shaped articles from foamed and unfoamed polystyrene sheets by thermoforming methods. As indicated above, many such articles are containers used for packaging foods or for the serving of foods. Polystyrene containers, however, are melted by hot fats and cannot be used to package fat-containing foods that are to be heated. Even when treated by radiation, the polystyrene containers still are not resistant to hot fats. This problem has been addressed in U.S. Pat. No. 4,205,114, which solves the problem by utilizing poly(p-methylstyrene) since it can be cross-linked by ionizing radiation to yield a cross-linked polymer which is resistant to the solvent action of fats.
The present invention has for its object a technique for the cross-linking of styrenic polymers in otherwise completed article form.